Robertson missed a good scoring chance early in the eighth frame

The Australian trailed 4-0 at one stage but battled back to 4-3 before missing a straightforward yellow in frame eight and Carter pounced with a break of 89.

He will next face Ronnie O'Sullivan, who beat 50-year-old veteran and fellow former world champion Steve Davis 5-3.

Former winner Stephen Hendry recovered from 4-3 down to squeeze past Ryan Day.

Robertson, who had been aiming to become only the third player, after O'Sullivan and Davis, to retain the title, was left to reflect on his lapse of concentration.

"I got ahead of myself and out of the present. That's the biggest mistake you can make in sport. It's a lesson to be learned," he said.

"When I got down over the yellow my concentration wasn't where it should've been. I was thinking about what I was going to say to the press afterwards. It was stupid."

I missed a few I should have potted, including one of the easiest pots you'll see Stephen Hendry

Hendry was playing in his 117th ranking quarter-final but his first since the Malta Cup 12 months ago.

"That was a good win, especially from 4-3 down," the Scot said.

"I missed a few I should have potted, including one of the easiest pots you'll see all week but when you're not 100% confident that's the kind of thing that plagues you.

"Confidence comes from winning so this result can only do me good."

The seven-times world champion, chasing his first silverware for three years, next meets Stephen Lee, a 5-2 conqueror of Michael Judge.

Shaun Murphy, who won last week's Malta Cup, continued his good recent run of form with a 5-2 win over Mark Williams, who is desperate for points having slumped to 33rd on the provisional world rankings.

Masters champion Mark Selby also made the quarter-finals, thanks to his 5-2 victory over Ken Doherty and will next face world champion John Higgins, who beat China's Ding Junhui 5-1.

World number 18 Joe Perry compiled back-to-back breaks of 107 and 115 on his way to beating Stuart Bingham 5-2.